Inspection apparatus and inspection method

ABSTRACT

An inspection apparatus for inspecting an inspection target surface arranged on an inspection plane, includes an X-ray generation tube having a target including an X-ray generation portion that generates X-rays by irradiation with an electron beam, and configured to emit X-rays to the inspection plane, and an X-ray detector configured to detect X-rays emitted from a foreign substance existing on the inspection target surface irradiated with the X-rays from the X-ray generation portion and totally reflected by the inspection target surface. The X-ray detector includes a long X-ray receiver.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation of International Patent ApplicationNo. PCT/JP2022/043906, filed on Nov. 29, 2022, which claims priority toand the benefit of Japanese Patent Application No. 2022-013653, filed onJan. 31, 2022, the entire disclosures of which are incorporated hereinby reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to an inspection apparatus and aninspection method.

Description of the Related Art

Japanese Patent Laid-Open No. 2009-236622 describes a high-resolutionX-ray microscope apparatus with an X-ray fluorescence analysis function,that includes a detector configured to detect fluorescent X-rays whichare generated from a sample by focusing electron beams on an X-raygeneration target by an object lens and irradiating the sample withX-rays generated from the target, and an analysis unit configured toanalyze the fluorescent X-rays from the detection result of thedetector. Japanese Patent Laid-Open No. 2009-236622 also describes anarrangement in which the whole detector or part of the detector isincorporated in the magnetic circuit of the object lens.

In recent years, for example, there has been a problem that a foreignsubstance having a size equal to or smaller than several tens of μm istaken in a product to cause a defect. For example, in a lithium ionbattery, with respect to a constituent member using carbon, copper, oraluminum as a material, a micronization of foreign substance ofstainless steel or part of the constituent member may be taken in thebattery at the time of manufacturing.

If, at the time of manufacturing a lithium ion battery, a foreignsubstance is taken in the battery, a separator for maintaininginsulation in the battery may break due to a vibration of the foreignsubstance after shipping of the battery. In this case, the battery maybe short-circuited to ignite or explode.

If a foreign substance can be detected nondestructively, it is possibleto prevent distribution of a product that may ignite or explode. As amethod of detecting a foreign substance existing on the surface of asample using X-rays and specifying the element of the foreign substance,there are provided X-ray Fluorescence (to also be called XRF) andGrazing Incidence X-ray Fluorescence (to also be called TXRF). In X-rayFluorescence, the element of a sample substrate is also excited. InGrazing Incidence X-ray Fluorescence, incident X-rays are scattered dueto a foreign substance. Therefore, in these measurement methods, thereis a problem that the intensity ratio of the generated fluorescentX-rays becomes low due to the foreign substance.

SUMMARY OF THE INVENTION

The present invention provides a technique advantageous in detecting aforeign substance existing on an inspection target surface with highsensitivity.

A first aspect of the present invention provides an inspection apparatusfor inspecting an inspection target surface arranged on an inspectionplane, comprising: an X-ray generation tube having a target including anX-ray generation portion that generates X-rays by irradiation with anelectron beam, and configured to emit X-rays to the inspection plane;and an X-ray detector configured to detect X-rays emitted from a foreignsubstance existing on the inspection target surface irradiated with theX-rays from the X-ray generation portion and totally reflected by theinspection target surface, wherein the X-ray detector includes a longX-ray receiver.

A second aspect of the present invention provides an inspectionapparatus for inspecting an inspection target object having a firstinspection target surface and a second inspection target surface,comprising: an X-ray generation tube having a target including an X-raygeneration portion that generates X-rays by irradiation with an electronbeam, and configured to emit X-rays to the inspection target object; andan X-ray detector including an X-ray receiver configured to receiveX-rays emitted from a foreign substance existing on the first inspectiontarget surface irradiated with the X-rays from the X-ray generationportion and totally reflected by the first inspection target surface andX-rays emitted from a foreign substance existing on the secondinspection target surface irradiated with the X-rays from the X-raygeneration portion and totally reflected by the second inspection targetsurface, wherein the X-ray receiver is arranged to intersect a firstvirtual plane including the first inspection target surface and a secondvirtual plane including the second inspection target surface.

A third aspect of the present invention provides an inspection method ofinspecting an inspection target surface arranged on an inspection plane,comprising: an X-ray detection step of emitting X-rays to the inspectionplane and detecting, by an X-ray detector including a long X-rayreceiver, X-rays emitted from a foreign substance existing on theinspection target surface and totally reflected by the inspection targetsurface; and a processing step of processing an output of the X-raydetector.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a view schematically showing the arrangement of an inspectionapparatus according to the first embodiment;

FIG. 2 is a view showing a practical example of the arrangement of theinspection apparatus according to the first embodiment;

FIG. 3 is a view schematically showing an example of the arrangement ofan X-ray generation tube;

FIG. 4 is an enlarged schematic view of part of the inspection apparatusshown in FIG. 2 ;

FIG. 5 is an enlarged schematic view of part of the inspection apparatusshown in FIG. 2 ;

FIG. 6 is a graph exemplifying the relationship between a distanceD_(xs) (abscissa) and the count (ordinate) of foreign substancesdetected by an X-ray detector;

FIG. 7 is a view showing a practical example of the arrangement of theinspection apparatus according to the embodiment;

FIG. 8 is a view for explaining a problem according to the secondembodiment;

FIG. 9 is a view schematically showing the arrangement of an inspectionapparatus according to the second embodiment; and

FIG. 10 is a view schematically showing the arrangement of an inspectionapparatus according to the third embodiment.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments will be described in detail with reference tothe attached drawings. Note, the following embodiments are not intendedto limit the scope of the claimed invention. Multiple features aredescribed in the embodiments, but limitation is not made to an inventionthat requires all such features, and multiple such features may becombined as appropriate. Furthermore, in the attached drawings, the samereference numerals are given to the same or similar configurations, andredundant description thereof is omitted.

FIG. 1 schematically shows the arrangement of an inspection apparatus IAaccording to the first embodiment of the present disclosure. Theinspection apparatus IA can be formed as, for example, an inspectionapparatus that inspects an inspection target surface TS arranged on aninspection plane IP. The inspection plane IP is a plane on which theinspection target surface TS should be arranged, and the inspectiontarget surface TS is one surface of an inspection target object IT. Theinspection apparatus IA can include an X-ray generation tube 101. TheX-ray generation tube 101 has a target (not shown) including an X-raygeneration portion XG that generates X-rays by irradiation with anelectron beam, and emits X-rays XR to the inspection plane IP. A foreignsubstance FS irradiated with the X-rays XR from the X-ray generationportion XG generates X-rays corresponding to a material forming theforeign substance FS, and such X-rays are also called fluorescent X-raysor characteristic X-rays. Some of the X-rays generated by the foreignsubstance FS irradiated with the X-rays XR are totally reflected by theinspection target surface TS. The X-rays emitted from the foreignsubstance FS and totally reflected by the inspection target surface TSare represented as X-rays XF. The inspection apparatus IA can include anX-ray detector 120. The X-ray detector 120 can be configured to detectthe X-rays XF emitted from the foreign substance FS existing on theinspection target surface TS irradiated with the X-rays XR from theX-ray generation portion XG and totally reflected by the inspectiontarget surface TS. The inspection apparatus IA can further include aprocessor that performs processing of detecting the foreign substance FSbased on an output from the X-ray detector 120. The processor canfurther perform processing of specifying the material forming theforeign substance FS based on the output from the X-ray detector 120.The processor can be implemented by, for example, a controller thatcontrols the operation of the inspection apparatus IA.

FIG. 2 shows a practical example of the arrangement of the inspectionapparatus IA shown in FIG. 1 . The inspection apparatus IA can includean X-ray generation apparatus 100, the X-ray detector 120, and acontroller 140. The X-ray generation apparatus 100 can include the X-raygeneration tube 101 and a driving circuit 103 that drives the X-raygeneration tube 101. The X-ray generation apparatus 100 can furtherinclude a boosting circuit 102 that supplies a boosted voltage to thedriving circuit 103. The X-ray generation apparatus 100 can furtherinclude a storage container (not shown) that stores the X-ray generationtube 101, the driving circuit 103, and the boosting circuit 102, and thestorage container can be filled with an insulating fluid such asinsulating oil. The controller 140 can be configured to control theX-ray generation apparatus 100 and the X-ray detector 120. Thecontroller 140 can have the function of the above-described processor.More specifically, the controller 140 can perform processing ofdetecting the foreign substance FS based on the output from the X-raydetector 120. Furthermore, the controller 140 can perform processing ofspecifying the material forming the foreign substance FS based on theoutput from the X-ray detector 120. The controller 140 can be formed by,for example, a PLD (an abbreviation of Programmable Logic Device) suchas an FPGA (an abbreviation of Field Programmable Gate Array), an ASIC(an abbreviation of Application Specific Integrated Circuit), ageneral-purpose or dedicated computer installed with a program, or acombination of all or some of these components.

The inspection apparatus IA may further include an X-ray detection panel130 that detects X-rays emitted from the X-ray generation portion XG andtransmitted through the inspection target object IT having theinspection target surface TS. The controller 140 can be configured togenerate an image (a transmission image of the inspection target objectIT) of the X-rays transmitted through the inspection target object ITbased on an output from the X-ray detection panel 130 and detect theforeign substance FS existing on the inspection target surface TS basedon the image. It is possible to detect a foreign substance existinginside the inspection target object IT and a foreign substance existingon a surface on the opposite side of the inspection target surface TSusing the X-ray detection panel 130. The controller 140 can beconfigured to detect the existence of the foreign substance FS and alsodetect the position and/or size of the foreign substance FS. Byproviding the X-ray detection panel 130 in addition to the X-raydetector 120, the foreign substance FS that cannot be detected by theX-ray detector 120 can be detected by the X-ray detection panel 130,thereby making it possible to improve the accuracy of detection of theforeign substance FS. As compared with a system including twoapparatuses that acquire a transmission image and detect a foreignsubstance, respectively, the inspection apparatus IA that acquires atransmission image and detects a foreign substance using X-rays emittedfrom one X-ray generation tube is advantageous in reducing the size andthe cost.

The inspection apparatus IA may further include a display 150, and thecontroller 140 can be configured to display, on the display 150,information indicating the constituent material of the foreign substanceFS specified based on the output from the X-ray detector 120. Thecontroller 140 can further be configured to display, on the display 150,the transmission image of the inspection target object IT generatedbased on the output from the X-ray detection panel 130. In addition, thecontroller 140 can be configured to display, on the display 150,information indicating the position and/or size of the foreign substancedetected based on the output from the X-ray detection panel 130. Thecontroller 140 may be formed by a single unit or may be divided into aplurality of units.

FIG. 3 schematically shows an example of the arrangement of the X-raygeneration tube 101. The X-ray generation tube 101 can include anelectron gun EG, an anode 93 having a target 933 including the X-raygeneration portion XG that generates X-rays when electrons from theelectron gun EG collide, and an insulating tube 92. In the X-raygeneration tube 101, the anode 93 can be arranged to close one of thetwo opening ends of the insulating tube 92, and a closing member 91including the electron gun EG can be arranged to close the other of thetwo opening ends of the insulating tube 92. A deflector 94 that deflectsthe flow (electron beam) of electrons from the electron gun EG may bearranged outside the insulating tube 92. The X-ray generation tube 101shown in FIG. 3 is an example of a sealed transmission type X-raygeneration tube in which the internal space of the insulating tube 92 ismaintained in a vacuum state and X-rays are transmitted through thetarget 933 and a target holding plate 932 (to be described later).However, as the X-ray generation tube 101, an unsealed open type ornon-transmission reflection type X-ray generation tube may be adopted.

The deflector 94 can be arranged outside the X-ray generation tube 101.With respect to a direction parallel to an axis AX of the X-raygeneration tube 101, the deflector 94 can be provided between the anode93 and a cathode (not shown). In an example, with respect to thedirection parallel to the axis AX of the X-ray generation tube 101, thedeflector 94 is provided between the electron gun EG and the target 933.More specifically, a virtual plane 97 crossing the deflector 94 can belocated in a space sandwiched between a virtual plane 95 contacting thedistal end of the electron gun EG and a virtual plane 96 contacting partof the target 933. The virtual planes 95, 96, and 97 are planesorthogonal to the axis AX of the X-ray generation tube 101.

The anode 93 can include the target 933, the target holding plate 932that holds the target 933, and an electrode 931 that holds the targetholding plate 932. The electrode 931 is electrically connected to thetarget 933 and can give a potential to the target 933. The target 933generates X-rays when electrons (electron beam) emitted from theelectron gun EG collide against the target 933. The X-ray generationportion XG is a portion of the surface of the target 933, against whichthe electrons (electron beam) collide. The X-rays generated by the X-raygeneration portion XG are transmitted through the target holding plate932 and emitted to the outside of the X-ray generation tube 101. Theanode 93 can be maintained at, for example, the ground potential but maybe maintained at another potential.

The target 933 is made of a metal material. The target 933 is desirablymade of a material having a high melting point, for example, tungsten,tantalum, molybdenum, or the like, which contributes to improvement ofX-ray generation efficiency. The target holding plate 932 can be made ofa material that readily passes X-rays, for example, beryllium, diamond,or the like. The target holding plate 932 is desirably made of diamond.This can decrease the thickness of the target holding plate 932 whilemaintaining the strength of the target holding plate 932, and candecrease the distance between the inspection plane IP (inspection targetsurface TS) and the target 933 (X-ray generation portion XG). Thethickness of the target holding plate 932 is desirably thin. Morespecifically, the thickness of the target holding plate 932 is desirably4 mm or less, and more desirably 2 mm or less, 1 mm or less, or 0.3 mmor less. The thickness of the target holding plate 932 can be set withreference to the distance from the X-ray generation portion XG to theinspection plane IP, which is necessary to specify an element containedin the foreign substance (to be described later). To specify the elementcontained in the foreign substance, the target holding plate 932 isdesirably, extremely thin. However, the target holding plate 932 isdesirably thick in terms of the processing cost and the individualdifference of the target holding plate 932, strength for maintaining theinternal space of the insulating tube 92 in the vacuum state, and thelike. Therefore, the optimum thickness of the target holding plate 932is desirably used. Note that FIG. 3 is not intended to show therelationship between the thickness of the target 933 and that of thetarget holding plate 932. For example, the thickness of the target 933may be several and the thickness of the target holding plate 932 may beseveral hundred μm.

FIG. 4 is an enlarged schematic view of part of the inspection apparatusIA shown in FIG. 2 . The foreign substance FS can exist on theinspection target surface TS. The X-rays (characteristic X-rays) XF thatare emitted from the foreign substance FS so as to be totally reflectedby the inspection target surface TS and are totally reflected by theinspection target surface TS enter an X-ray receiver 121 of the X-raydetector 120. On the other hand, fluorescent X-rays that can begenerated from the inspection target object IT by irradiation with theX-rays XR from the X-ray generation portion XG hardly enter the X-rayreceiver 121 of the X-ray detector 120 arranged to detect the X-rays(characteristic X-rays) XF. Therefore, the ratio of the fluorescentX-rays emitted from the inspection target object IT and detected by theX-ray detector 120 with respect to the X-rays (characteristic X-rays) XFemitted from the foreign substance FS and detected by the X-ray detector120 can be made extremely low.

The X-ray detector 120 may be a silicon drift detector (SDD), a CdTedetector, or a CdZnTe detector. The X-ray detector 120 may be an energydispersion detector. If the X-ray detector 120 is an energy dispersiondetector, the controller (or processor) 140 can decide the material orelement forming the foreign substance FS based on the elemental profileof energy dispersion (a count value for each energy). Commercialsoftware may be installed on the controller (or processor) 140 to decidethe material or element forming the foreign substance FS. Examples ofsuch software are, for example, “XRS-FP Quantitative XRF AnalysisSoftware” of AMETEK or UniQuant software.

The specifications of the X-ray detector 120 can be decided inaccordance with an energy resolution necessary to detect a foreignsubstance. An example of a detector having a low energy resolution canbe a detector using a scintillator, an Si PIN photodiode, or a CCD. Anexample of a detector having an even higher energy resolution can be adetector using a proportional counter. An example of a detector havingan even higher energy resolution can be a detector applied with a CdTedirect-bandgap crystal or an energy dispersion detection method like anSi drift detector. An example of a detector having an even higher energyresolution can be a detector applied with a wavelength dispersiondetection method of obtaining energy from an angle using an analyzingcrystal.

To totally reflect, by the inspection target surface TS, the fluorescentX-rays from the foreign substance FS, an angle at which the fluorescentX-rays from the foreign substance FS enter the inspection target surfaceTS needs to be a total reflection critical angle θ_(c) or less.

$\begin{matrix}{\delta = {\left( \frac{r_{e}\lambda^{2}}{2\pi} \right)N_{0}\rho{\sum\limits_{i}{{x_{i}\left( {z_{i} + f_{i}^{\prime}} \right)}/{\sum\limits_{i}{x_{i}M_{i}}}}}}} & (1) \\{\theta_{c} \approx \sqrt{2\delta}} & \end{matrix}$

-   -   θ_(c): total reflection critical angle    -   r_(e): classical electron radius (2.818×10⁻¹⁵ m)    -   N₀: Avogadro number    -   λ: X-ray wavelength    -   ρ: density (g/cm³)    -   Zi, Mi, xi: atomic number, atomic weight, and atomic ratio        (molar ratio) of ith atom    -   f_(i): atomic scattering factor (anomalous dispersion term) of        ith atom

If the inspection target surface TS is made of a metal, the totalreflection critical angle is theoretically about 1° or less. However, infact, the metal surface is often oxidized or carbonized, or a reflectioncritical angle different from the theoretical value is often obtainedbecause, for example, the surface is covered with a graphite layer. If atotal reflection condition is satisfied when the inspection targetsurface TS is irradiated with the X-rays XR, an angle (total reflectioncritical angle) formed by the inspection target surface TS and thecharacteristic X-rays XF emitted from the foreign substance FS andtotally reflected by the inspection target surface TS is confirmed to be5° or less through an experiment. At this time, since the foreignsubstance FS is extremely small as compared with a distance D_(xs)between the X-ray generation portion XG and the inspection plane IP(inspection target surface TS), a position at which the X-rays emittedfrom the foreign substance FS are totally reflected by the inspectiontarget surface TS may be regarded as a position at which the X-rays XRfrom the X-ray generation portion XG enter the inspection plane IP. Ifthe foreign substance FS exists at a position where the X-rays XR fromthe X-ray generation portion XG vertically enter the inspection planeIP, as shown in FIG. 4 , the position at which the X-rays emitted fromthe foreign substance FS are totally reflected by the inspection targetsurface TS may be regarded as the position at which the X-rays XR fromthe X-ray generation portion XG vertically enter the inspection planeIP.

Since the total reflection critical angle is 5° or less, an angle θformed by the inspection plane IP and a virtual line connecting theX-ray receiver 121 of the X-ray detector 120 and the position at whichthe X-rays XR from the X-ray generation portion XG enter the inspectionplane IP (an angle formed by the inspection plane IP and a virtual lineconnecting the center of the X-ray receiver of the X-ray detector 120and the intersection point of the inspection plane IP and the axis ofthe X-ray generation tube 101) can be set to 5° or less, desirably 2° orless, and more desirably 1° or less. As the angle θ is smaller, theratio of the fluorescent X-rays emitted from the inspection targetobject IT and detected by the X-ray detector 120 with respect to theX-rays (characteristic X-rays)XF emitted from the foreign substance FSand detected by the X-ray detector 120 can be made lower.

The X-ray detector 120 can be arranged at a position where the extensionplane of the inspection plane IP crosses the X-ray detector 120. Asschematically shown in FIG. 5 , the X-ray receiver 121 can include awindow portion 122 that passes the X-rays XF. The window portion 122 canhave, for example, a diameter of several mm and a thickness of severalhundred μm. The window portion 122 can be made of, for example,beryllium. As schematically shown in FIG. 5 , the inspection apparatusIA may include a slit member 125 having a slit (opening) on a virtualline connecting the X-ray receiver 121 of the X-ray detector 120 and theposition at which the X-rays XR from the X-ray generation portion XGenter the inspection plane IP. The size of the slit provided in the slitmember 125 and the arrangement position of the X-ray detector 120 can bedecided in accordance with a range irradiated with the X-rays XR on theinspection target surface TS, the materials that can form the inspectiontarget surface TS and the foreign substance FS, and the like. Consider acase in which foreign substances FS1 and FS3 exist at two ends of awidth Y irradiated with the X-rays XR on the inspection target surfaceTS, and a distance Z from the center of the width Y to the X-rayreceiver 121 has the same length as that of the width Y, asschematically shown in FIG. 7 . In this case, by setting the lower limitof a width W_(s) of the slit to Y×tan θ, and setting a distance X₂between the center of the X-ray receiver 121 and the inspection plane IPto Y×tan θ, it is possible to detect all foreign substances within therange irradiated with the X-rays XR on the inspection target surface TS.

To increase the intensity of the X-rays XF detected by the X-raydetector 120, the distance D_(xs) from the X-ray generation portion XGto the inspection plane IP is desirably made small. FIG. 6 shows aresult of obtaining, by an experiment, the relationship between thedistance D_(xs) (abscissa) and the count (ordinate) of foreignsubstances FS detected by the X-ray detector 120. The count is a totalcount (peak count), per predetermined time, of energy corresponding tothe position of fluorescent X-rays (for example, Ni Kα-rays) exitingfrom a specific element contained in the foreign substance. Consideringa count TH necessary to specify the element, the distance D_(xs) fromthe X-ray generation portion XG to the inspection plane IP is desirably5 mm or less, more desirably 4 mm or less, and still more desirably 3 mmor less. As the X-ray generation tube 101, for example, a sealedtransmission microfocus X-ray source of Canon ANELVA, more specifically,the G series, and still more specifically, the G-511 series or G-311series is useful.

To detect, by a transmission image, a foreign substance having a size ofseveral μm to several tens of μm with high sensitivity, a distanceD_(sf) from the inspection plane IP to the X-ray detection panel 130needs to be made sufficiently larger than D_(xs). For example, if 10pixels are necessary to detect a foreign substance having a diameter of5 when an X-ray detection panel (FPD) having a pixel pitch of 100 μm isused, a magnification ratio of 100×10/5=200 is required for detection.As for a foreign substance having a diameter of 50 μm, a magnificationratio of 20 is required for detection. Therefore, D_(sf)/D_(xs) is setto desirably 20 or more, and more desirably 200 or more. This can detecta foreign substance with high sensitivity using a transmission image.

The inspection apparatus IA is useful to detect a foreign substanceattached to a material of a lithium ion battery in a manufacturing stepof the lithium ion battery, but is merely an example and is also usefulfor other application purposes. For example, the inspection apparatus IAmay be used to measure and analyze airborne particles such as PM2.5influencing the environment and health. In this case, by using theinspection apparatus IA for the conventional technique of periodically(for example, every hour or every day) measuring the number of particlesand the sizes of the particles, it is possible to simultaneously specifymaterials or elements forming the particles in addition to measurementof the number of particles and the sizes of the particles, therebyimplementing more advanced environmental and health measures.Alternatively, by using the inspection apparatus IA for the field ofsemiconductors, micronization of which has recently been advanced, suchas an “EUV mask manufacturing apparatus, an inspection apparatus, and aninspection apparatus of a semiconductor manufacturing step, it ispossible to improve a yield and early solve the cause of an abnormalityusing the element information of a foreign substance.

An inspection method of inspecting the inspection target surface TSarranged on the inspection plane IP using the inspection apparatus IAwill be described below. The inspection method can include an X-raydetection step of emitting X-rays to the inspection plane IP (inspectiontarget surface TS) and detecting, by the X-ray detector 120, the X-raysXF emitted from the foreign substance FS existing on the inspectiontarget surface TS and totally reflected by the inspection target surfaceTS, and a processing step of processing an output of the X-ray detector120. The processing step can include a step of detecting the foreignsubstance FS and/or a step of specifying a material forming the foreignsubstance FS. The inspection method can further include a step ofdetecting, by the X-ray detection panel 130, X-rays transmitted throughthe inspection target object IT having the inspection target surface TS,and in the processing step, the output of the X-ray detector 120 and anoutput of the X-ray detection panel 130 can be processed. The processingstep can include a step of detecting the existence of the foreignsubstance FS and the position of the foreign substance FS based on theoutput of the X-ray detection panel 130. Alternatively, the processingstep can include a step of detecting the existence of the foreignsubstance FS, the position of the foreign substance FS, and the size ofthe foreign substance FS based on the output of the X-ray detectionpanel 130.

FIG. 9 schematically shows the arrangement of an inspection apparatus IAaccording to the second embodiment. Matters not mentioned in the secondembodiment can comply with the first embodiment. FIG. 9 shows X-rays XF11 and XF12 emitted from a foreign substance FS1 and totally reflectedby an inspection target surface TS. The inspection apparatus IAaccording to the second embodiment can include an X-ray detector 1205including a long X-ray receiver 1206 that extends in a predetermineddirection. In the example shown in FIG. 9 , the X-ray receiver 1206extends in a direction parallel to a surface parallel to the inspectiontarget surface TS. From another viewpoint, the X-ray receiver 1206extends in a direction parallel to the longitudinal direction of aninspection target object IT. From still another viewpoint, the X-rayreceiver 1206 extends in a direction parallel to a conveyance directionDIR of the inspection target object IT by a conveyance mechanism CV. TheX-ray receiver 1206 can have a rectangular shape having short and longsides, and the longitudinal direction is a direction parallel to thelong side. The long side can have, for example, a length which is threeor more times longer than the short side.

Although not shown in FIG. 9 , the inspection apparatus IA may include aslit member having a slit, and the slit member can have a rectangularshape that extends along the longitudinal direction of the X-rayreceiver 1206. The slit may be divided into a plurality of partial slitsand then arranged. The slit member is advantageous in improving thedetection accuracy of a foreign substance. Furthermore, by providing theslit member, it is possible to specify the position of a foreignsubstance based on the positional relationship between the X-rayreceiver 1206 and the slit.

The long X-ray receiver 1206 is advantageous in detecting the foreignsubstance FS1 even in a case where some of the X-rays emitted from theforeign substance FS1 and totally reflected by the inspection targetsurface TS are blocked by another foreign substance FS2. In an exampleshown as a reference in FIG. 8 , the X-rays XF11 emitted from theforeign substance FS1 and totally reflected by the inspection targetsurface TS can be blocked by the foreign substance FS2. However, in theinspection apparatus IA according to the second embodiment shown in FIG.9 , the X-rays XF12 emitted from the foreign substance FS1 and totallyreflected by the inspection target surface TS can enter the X-rayreceiver 1206. Although not shown in FIG. 9 , the longitudinal directionof the X-ray receiver 1206 may be parallel to a direction intersectingthe inspection plane IP or may be parallel to a direction orthogonal tothe inspection plane IP.

FIG. 10 schematically shows the arrangement of an inspection apparatusIA according to the third embodiment. Matters not mentioned in the thirdembodiment can comply with the first or second embodiment. Theinspection apparatus IA according to the third embodiment is configuredto inspect an inspection target object IT having a first inspectiontarget surface TS1 and a second inspection target surface TS2. The firstinspection target surface TS1 and the second inspection target surfaceTS2 can be opposite surfaces of the inspection target object IT. Theinspection apparatus IA includes an X-ray generation tube 101, and theX-ray generation tube 101 has a target including an X-ray generationportion XG that generates X-rays by irradiation with an electron beam,and emits X-rays XR to the inspection target object IT. The inspectionapparatus IA includes an X-ray detector 1201. The X-ray detector 1201includes an X-ray receiver 1211. The X-ray receiver 1211 receives X-raysXF11 emitted from a foreign substance FS1 existing on the firstinspection target surface TS1 irradiated with the X-rays XR from theX-ray generation portion XG and totally reflected by the firstinspection target surface TS1 and X-rays XF12 emitted from a foreignsubstance FS2 existing on the second inspection target surface TS2irradiated with the X-rays XR from the X-ray generation portion XG andtotally reflected by the second inspection target surface TS2. The X-rayreceiver 1211 can be arranged to intersect a first virtual plane IP1including the first inspection target surface TS1 and a second virtualplane IP2 including the second inspection target surface TS2. In otherwords, the X-ray receiver 1211 can have an area or a spread thatintersects the first virtual plane IP1 including the first inspectiontarget surface TS1 and the second virtual plane IP2 including the secondinspection target surface TS2. The first inspection target surface TS1and the second inspection target surface TS2 can be arrangedsymmetrically with respect to a virtual plane VP. The first X-rayreceiver 1211 and a second X-ray receiver 1222 can be arranged to faceeach other via the virtual plane VP. In FIG. 10 , the inspection targetobject IT can be conveyed by a conveyance mechanism (not shown) in adirection orthogonal to the paper surface. The virtual plane VP can beset to be parallel to the conveyance direction of the inspection targetobject IT by the conveyance mechanism. According to the thirdembodiment, it is possible to inspect two surfaces of the inspectiontarget object IT.

The inspection apparatus IA may include slit members 1251 and 1252 thatlimit the X-rays XF11 and XF12 entering the X-ray receiver 1211,respectively. The X-rays XF11 and XF12 can pass through slits formed inthe slit members 1251 and 1252, respectively, thereby entering the X-rayreceiver 1211. The slit members 1251 and 1252 may be integrated.

The present invention is not limited to the above embodiments andvarious changes and modifications can be made within the spirit andscope of the present invention. Therefore, to apprise the public of thescope of the present invention, the following claims are made.

What is claimed is:
 1. An inspection apparatus for inspecting aninspection target surface arranged on an inspection plane, comprising:an X-ray generation tube having a target including an X-ray generationportion that generates X-rays by irradiation with an electron beam, andconfigured to emit X-rays to the inspection plane; and an X-ray detectorconfigured to detect X-rays emitted from a foreign substance existing onthe inspection target surface irradiated with the X-rays from the X-raygeneration portion and totally reflected by the inspection targetsurface, wherein the X-ray detector includes a long X-ray receiver. 2.The inspection apparatus according to claim 1, further comprising aprocessor configured to perform processing of detecting the foreignsubstance based on an output from the X-ray detector.
 3. The inspectionapparatus according to claim 2, wherein that the processor furtherperforms processing of specifying a material forming the foreignsubstance.
 4. The inspection apparatus according to claim 1, whereinthat a distance between the inspection plane and the X-ray generationportion is not larger than 5 mm.
 5. The inspection apparatus accordingto claim 1, wherein that a distance between the inspection plane and theX-ray generation portion is not larger than 3 mm.
 6. The inspectionapparatus according to claim 1, wherein that an angle formed by theinspection plane and a virtual line connecting a center of the X-rayreceiver and an intersection point of the inspection plane and an axisof the X-ray generation tube is not larger than 5°.
 7. The inspectionapparatus according to claim 1, wherein that an angle formed by theinspection plane and a virtual line connecting a center of the X-rayreceiver and an intersection point of the inspection plane and an axisof the X-ray generation tube is not larger than 2°.
 8. The inspectionapparatus according to claim 6, further comprising a slit member havinga slit on the virtual line.
 9. The inspection apparatus according toclaim 1, further comprising an X-ray detection panel configured todetect X-rays emitted from the X-ray generation portion and transmittedthrough an inspection target object having the inspection targetsurface.
 10. The inspection apparatus according to claim 1, wherein thatthe X-ray generation tube is of a sealed transmission type.
 11. Theinspection apparatus according to claim 1, wherein that the X-raygeneration tube includes a target holding plate configured to hold thetarget, and a thickness of the target holding plate is not larger than 4mm.
 12. The inspection apparatus according to claim 11, wherein that thetarget holding plate contains diamond.
 13. The inspection apparatusaccording to claim 1, wherein that a longitudinal direction of the X-rayreceiver is parallel to a surface parallel to the inspection targetsurface.
 14. The inspection apparatus according to claim 13, furthercomprising a conveyance mechanism configured to convey an inspectiontarget object having the inspection target surface, wherein theconveyance mechanism conveys the inspection target object in aconveyance direction parallel to the inspection plane, and thelongitudinal direction is parallel to the conveyance direction.
 15. Theinspection apparatus according to claim 1, wherein that a longitudinaldirection of the X-ray receiver is parallel to a direction intersectingthe inspection plane.
 16. The inspection apparatus according to claim 1,wherein that a longitudinal direction of the X-ray receiver is parallelto a direction orthogonal to the inspection plane.
 17. An inspectionapparatus for inspecting an inspection target object having a firstinspection target surface and a second inspection target surface,comprising: an X-ray generation tube having a target including an X-raygeneration portion that generates X-rays by irradiation with an electronbeam, and configured to emit X-rays to the inspection target object; andan X-ray detector including an X-ray receiver configured to receiveX-rays emitted from a foreign substance existing on the first inspectiontarget surface irradiated with the X-rays from the X-ray generationportion and totally reflected by the first inspection target surface andX-rays emitted from a foreign substance existing on the secondinspection target surface irradiated with the X-rays from the X-raygeneration portion and totally reflected by the second inspection targetsurface, wherein the X-ray receiver is arranged to intersect a firstvirtual plane including the first inspection target surface and a secondvirtual plane including the second inspection target surface.
 18. Aninspection method of inspecting an inspection target surface arranged onan inspection plane, comprising: an X-ray detection step of emittingX-rays to the inspection plane and detecting, by an X-ray detectorincluding a long X-ray receiver, X-rays emitted from a foreign substanceexisting on the inspection target surface and totally reflected by theinspection target surface; and a processing step of processing an outputof the X-ray detector.
 19. The inspection method according to claim 18,wherein the processing step includes a step of detecting the foreignsubstance.
 20. The inspection method according to claim 18, wherein theprocessing step includes a step of specifying a material forming theforeign substance.
 21. The inspection method according to claim 18,further comprising a step of detecting, by an X-ray detection panel,X-rays transmitted through an inspection target object having theinspection target surface, wherein in the processing step, the output ofthe X-ray detector and an output of the X-ray detection panel areprocessed.
 22. The inspection method according to claim 21, wherein theprocessing step includes a step of detecting existence of the foreignsubstance and a position of the foreign substance based on the output ofthe X-ray detection panel.
 23. The inspection method according to claim21, wherein the processing step includes a step of detecting existenceof the foreign substance, a position of the foreign substance, and asize of the foreign substance based on the output of the X-ray detectionpanel.